The field of the invention relates to shield systems for protecting against accidental needle stick injury.
Syringes are well known medical devices for administering medicaments to patients. Prefilled syringes are generally considered as those which are filled with a selected dosage of medicament by a pharmaceutical manufacturer for distribution to the end user. They are often comprised of a glass or plastic barrel which contains the medicament and a piston slidably mounted within the barrel. One end of the barrel includes a needle or the like affixed thereto or a connector for a needle assembly such as a Luer fitting. The other end of the syringe is open to allow the insertion of a plunger rod. The plunger rod allows the user to apply manual force to the piston, causing the medicament to be delivered through the needle or other piercing element.
The use of a sharp-pointed piercing element entails the risk of accidental needle stick. To avoid such accidents, many prior art hypodermic syringes have included rigid cylindrical safety shields telescoped over the syringe barrel. These shields can be moved between retracted positions where the needles are exposed for use, to extended positions where the needles are surrounded by the shields. U.S. Pat. Nos. 4,425,120, 4,573,976, 4,850,994 and 4,923,447 disclose various shield systems for hypodermic syringes. The latter two patents disclose shields which are spring-actuated. It is ordinarily desirable to lock the needle shields in the protected positions, and a number of prior art designs provide for such locking. Some systems, such as those disclosed in U.S. Pat. Nos. 5,201,708, 5,242,240 and 5,318,538 are designed to allow the shields to be retracted from their locked, extended positions.
A shield system for protecting the piercing element of a prefilled syringe is disclosed in European Publication No. EP 0 740 942 A1. The disclosed system includes a holder which is coupled to the flange of the syringe barrel, and a shield which is telescopically mounted to the holder. Two hands are required to operate this system.